Why are cells microscopic? The answer relates to the needs for the cell to effectively move materials in and remove waste. In this activity, students will create simulated cells (agar blocks) of different sizes and examine how effectively a substance is able to diffuse into the cell in a set period of time. A special indicator in the cells will allow students to visualize the degree of diffusion. The results will clearly display the fact that a smaller volume creates a more favorable condition for the exchange of material across a cell membrane. Kit contains enough materials for 15 groups of students. Teacher's Manual and Student Study Guide copymasters are included.